Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
  • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
  • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
  • A61B17/68—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin
  • A61B17/80—Cortical plates, i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L31/00—Materials for other surgical articles, e.g. stents, stent-grafts, shunts, surgical drapes, guide wires, materials for adhesion prevention, occluding devices, surgical gloves, tissue fixation devices
  • A61L31/12—Composite materials, i.e. containing one material dispersed in a matrix of the same or different material
  • A61L31/125—Composite materials, i.e. containing one material dispersed in a matrix of the same or different material having a macromolecular matrix
  • A61L31/126—Composite materials, i.e. containing one material dispersed in a matrix of the same or different material having a macromolecular matrix containing carbon fillers
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
  • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
  • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
  • A61B17/68—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin
  • A61B17/80—Cortical plates, i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates
  • A61B17/8052—Cortical plates, i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates immobilised relative to screws by interlocking form of the heads and plate holes, e.g. conical or threaded
  • A61B17/8057—Cortical plates, i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates immobilised relative to screws by interlocking form of the heads and plate holes, e.g. conical or threaded the interlocking form comprising a thread
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
  • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
  • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
  • A61B17/68—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin
  • A61B17/84—Fasteners therefor or fasteners being internal fixation devices
  • A61B17/86—Pins or screws or threaded wires; nuts therefor
  • A61B17/8625—Shanks, i.e. parts contacting bone tissue
  • A61B17/863—Shanks, i.e. parts contacting bone tissue with thread interrupted or changing its form along shank, other than constant taper
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
  • A61B2017/00526—Methods of manufacturing
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L2430/00—Materials or treatment for tissue regeneration
  • A61L2430/02—Materials or treatment for tissue regeneration for reconstruction of bones; weight-bearing implants

Definitions

• the present invention concerns an osteo-synthesis device formed by a suitably shaped plate able to be attached, by means of orthopedic screws, on bone fragments in order to re-compose them.
• the plate is made of titanium, for example. or other bio-compatible metal materials, and is attached on the bone fragments with suitable orthopedic attachment screws.
• the European patent application EP-A-2. 147.647 describes an osteo-synthesis plate made of composite material with a polyether ether ketone (PEEK) base, reinforced by carbon fibers, suitable to be attached on the bone fragments by means of orthopedic screws inserted into through holes made through the plate.
• PEEK is a semi-crystalline thermoplastic polymer with good stability at high temperatures, resistance to damage caused by exposure to chemical agents and/or ionizing radiations and compatible with different reinforcing agents (glass fiber and carbon fiber).
• PEEK a suitable material for making orthopedic devices.
• orthopedic screws are the polyaxial type, that is, they can be attached with different angular positions, thus allowing the orthopedic surgeon to make adjustments.
• Patent application US-A-2009248087 describes an osteo-synthesis device formed by a titanium plate having threaded through holes to insert orthopedic screws.
• Annular clamping inserts are disposed in the threaded holes, made of softer bio-compatible material than the material that forms the plate, for example PEEK, or UHMWPE ("ultra high molecular weight polyethylene”), or a softer metal than that of the plate.
• PEEK polyethylene
• UHMWPE ultra high molecular weight polyethylene
• the European patent EP-B- 1 .555.943 describes a self-clamping osteo- synthesis device with a plate provided with holes for the passage of attachment screws.
• the plate is the composite type, that is, the edges of the holes are formed by inserts made of bio-compatible plastic material, typically PEEK, with self- threading mechanical properties by means of the screws.
• the remaining part of the plate is made of metal, ty pically titanium;
• PEEK in itself may not offer adequate attachment resistance in cooperation with the attachment screws, and therefore the coupling may not be sufficiently secure.
• the solutions in which, substantially for self-threading purposes, the attachment screws deform the inner wall of the holes or of the inserts inserted in the holes have the disadvantage of the debris caused by this excavation operation, which may remain trapped between the screw and the plate in contact with the biological tissue.
• the debris is a chip-like material which may be bio-compatible, but in any case it is preferable, in surgical practice, to avoid it. This situation is often unwanted in the surgical field in question, particularly if the debris also comprises residual materials such as carbon fibers.
• Purpose of the present invention is to obtain an osteo-synthesis device that is bio-compatible, that allows to use polyaxial screws and that ensures a secure and resistant coupling of the plate and the attachment screws.
• the Applicant has devised, tested and embodied the present invention to , overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.
• an osteo-synthesis device is used to recompose bone fractures in the surgical field and comprises an osteo-synthesis plate prov ided with through holes into which attachment inserts are inserted stably or constrained, for example by screw ing, into each of which inserts an orthopedic attachment screw is inserted.
• the material the attachment inserts are made of is a bio-compatible material which advantageously has mechanical properties such as to allow them to be self- threaded by screwing in the attachment screws.
• the material that the attachment inserts are made of is a composite material formed by a polymeric matrix in which reinforcement elements, having a different chemical composition from that of the polymeric matrix, are inserted or drowned.
• the composite material used in the present invention has good resistance, rigidity and resistance to cracks.
• the material the attachment inserts are made of is formed by polyether ether ketone (PEEK) reinforced with carbon fibers.
• PEEK polyether ether ketone
• the PEEK is reinforced with carbon fibers in a range between about 20% and about 70% in weight, preferably between about 25% and about 65% in weight.
• One form of embodiment provides PEEK reinforced with carbon fibers at 30% or 35% in weight.
• Another form of embodiment provides PEEK reinforced with carbon fibers at 60% in weight.
• the increased mechanical resistance of the attachment inserts made according to the present invention allows to provide inserts with a bigger outer diameter than that commonly used in the state of the art, w hile the inner diameter continues to be determined by the need to cooperate with the attachment screws.
• This possibility has the advantage that it increases the radio-transparency window of the osteo-synthesis dev ice and hence improves the radiographic analyses for verifying and monitoring the screw implant, especially the polyaxial ones, and also the re-composition of the bone. This requirement is even more keenly felt when the plate is made of metal, which is not radio-transparent, because in an X-ray the visibility in radio-transparency would be limited only to the attachment holes, and therefore not optimal.
• attachment inserts of a composite material formed by a polymeric matrix in which reinforcement elements are inserted or drowned has the advantage that it allows easy removal of the orthopedic screws when it is necessary to remove the plate when the bone fracture has finished its re- composition: such screws, which can also be made of bio-compatible metal, if screwed directly to the metal of the plate, are substantially fused with it. On the contrary, screws screwed onto the composite material according to the present invention do not adhere and can be removed more easily.
• the material the plate is made of can be a biocompatible metal, such as titanium or its alloys, or a polymeric material, such as PEEK, or a composite material formed by a polymeric matrix in which reinforcement elements are inserted or drowned, such as PEEK reinforced with carbon fibers, for example as described above.
• the through holes in the plate are threaded internally, to cooperate with the attachment inserts that, in some forms of embodiment, may be pre-threaded externally in a mating manner.
• the attachment inserts also have internally a pre-threading that can facilitate the operation of screwing the orthopedic screws.
• This solution considerably reduces the phenomenon, generally unwanted, of the formation of debris, particularly for solutions where the reinforcement elements are carbon fibers, even more particularly in solutions where the percentage in weight of the carbon fibers is high, for example about 60% in weight, and the excavation of the attachment insert by the screw could expose a very fine debris with a carbon fiber base to the biological tissues.
• the present invention also concerns an attachment pre-insert suitable to be inserted in a through hole of a plate of an osteo-synthesis device of the type in question.
• the attachment pre-insert according to the present invention is made of composite material formed by a polymeric matrix in which reinforcement elements are inserted or drowned.
• the attachment pre-insert is formed by at least two parts, of which a first part is shaped to cooperate in coupling with a screwing tool, and a second part is shaped to cooperate, for example in screwing, with the through hole, and is suitable to define, during use, an attachment insert which has one or more attachment holes, into each of which an orthopedic attachment screw is inserted, said second part advantageously having an outer threading suitable to cooperate with a threading made inside the attachment hole.
• the axial extension of the second part is substantially the same as, or smaller than, the depth of the through hole, while the extension of the first part is correlated to the type of screwing tool with which it is suitable to cooperate.
• the embodiment with the composite material by increasing the mechanical resistance, allows to use screwing tools and to apply a suitable clamping force without damaging the insert itself.
• the attachment pre-insert has been inserted and constrained, for example by means of screwing, into the through hole, by acting on the relative first part, the first part protruding from the surface of the plate is completely eliminated, for example by means of a mechanical operation to remove material, such as milling, whereas the second part, which will define the final attachment insert, is constrained, for example screwed, into the through hole, and remains flush w ith or below the surface, so that it does not protrude and is incorporated into the plate.
• the plate is made of polymeric material, such as PEEK, or polymeric composite, such as PEEK reinforced w ith carbon fibers, it can alternatively be made:
• - fig. 1 is a plan view of an osteo-synthesis device according to the present invention: - fig. 2 is a lateral view of an attachment pre-insert according to the present invention;
• - fig. 3 is a plan view of fig. 2;
• - fig. 4 is an enlarged detail of fig. 1 ;
• - fig. 5 is a section of fig. 4;
• FIG. 6 is a diagram of a first assembly step of an attachment insert into a plate of an osteo-synthesis device according to the present invention
• - fig. 7 is a section of fig. 4;
• FIG. 8 is a diagram of a second working step of an attachment insert in a plate of an osteo-synthesis device according to the present invention.
• - fig. 9 is a section of fig. 7;
• - fig. 10 is a plan view of the detail in fig. 4 associated w ith an orthopedic attachment screw disposed perpendicular;
• - figs. 1 1 to 13 are sections of the detail in fig. 4 associated with orthopedic screws with different angular inclinations of their axis with respect to the plane of the plate;
• - fig. 14 is a plan view of the detail in fig. 4 associated with an orthopedic attachment screw disposed inclined;
• - fig. 15 is a schematic representation of an X-ray of fig. 14;
• - fig. 16 is a plan view of a variant of the osteo-synthesis device according to the present invention.
• - fig. 17 is a schematic representation of a composite material according to the present invention formed by a polymeric matrix in which reinforcement fibers are inserted;
• - fig. 1 8 is a comparative graph of the mechanical properties of elastomers, polymers, bone cortex, metals, composite materials and ceramics;
• - fig. 19 is a comparative graph of the resistance to traction for bone cortex, composite PEEK reinforced with carbon fibers, PEEK, polyethylene;
• - fig. 20 is a comparative graph of the resistance to flexion of PEEK reinforced with carbon fibers compared with other materials.
• the through holes 12 of the plate 1 1 are threaded internally, to allow attachment by screw ing the attachment inserts 14 inside them.
• the plate 1 1 is made for example of titanium.
• Each attachment insert 14 is axial-symmetrical w ith respect to a central axis Y, around which it develops, with a first segment 1 8 and a second segment 20 which delimit the relative attachment hole 16 (fig. 5).
• the first segment 1 8 is flared, converging toward the inside of the plate, whose walls have in section (fig. 5) an angular incl ination with respect to the central axis Y comprised between about 40° and 50°, for example about 45°, so that the overall angular amplitude of the first segment 1 8 is comprised between about 80° and about 100°, for example 90°.
• the second segment 20 has a linear development substantially parallel to the axis Y from the first segment 1 8 toward the outside of the plate 1 1 .
• the attachment holes 16 can have internally a pre-threading, to facilitate the screwing of the orthopedic screws 36.
• the attachment inserts 16 can have externally a pre-threading, to facilitate screwing into the through holes 12.
• each insert 14 is made of a composite polymeric material formed by a polymeric matrix 50 in which reinforcement elements 60 are drowned, having a di fferent chemical composition from that of the polymeric matrix (fig. 1 7).
• the polymeric matrix of the composite material is polyether ether ketone (PEEK).
• the reinforcement elements are carbon fibers. of the desired length, for example about 6 mm, or with a distribution of lengths comprised between a maximum length and a minimum length, for example a Gaussian distribution of fiber lengths, or a desired percentage ratio between a first length and a second length, shorter, according to needs.
• the disposition of the fibers can be ordered, in a longitudinal or transverse direction, or can be the statistical type.
• the carbon fibers can be pre-impregnated by a resin or binder, of a know n type.
• Fig. 1 7 is a schematic representation of a polymeric matrix 50 in which reinforcement fibers 60 are inserted.
• a composite material that can be used is formed by PEEK, commercially available from INVIBIO w ith the name of PEEK-OPTIMA® combined with short reinforcement carbon fibers.
• the polymeric matrix is loaded with about 30% or 35% in weight of reinforcement elements. In other forms of embodiment, the polymeric matrix is loaded with about 60% in weight of reinforcement elements.
• the present invention also concerns an attachment pre-insert 24 (figs. 2 and 3), produced using the composite material w ith polymeric matrix as described above, with inner reinforcement elements.
• the attachment pre-insert 24 was developed by Applicant to allow the insertion and screwing of the attachment insert 14 in the attachment holes.
• the attachment pre-insert 24 is coupled with the plate 1 1 and then worked to obtain from it the finished form of the attachment insert 14.
• the attachment pre-insert 24 comprises a first portion 26 and a second portion 28, disposed one above the other along the central axis Y.
• the first portion 26 is configured to be driven by a screwing tool 32 (figs. 6, 7), for example in this case with a hexagonal head to be driven by a suitable key, allow ing to screw the attachment pre-insert 24 into a through hole 1 2 of the plate 1 1 .
• a screwing tool 32 figs. 6, 7
• other conformations of the first portion 26 are possible, for example with a notch or cross for use with a corresponding traditional screwdriver, or with a recessed seat, hexagonal, star-shaped or other, for use with a key or special screw driver.
• the second portion 28, instead, has a shape corresponding substantially to the shape of the attachment insert 14.
• the attachment pre-insert 24 can be made directly with a through axial cavity 30, possibly pre-threaded, for insertion of the relative orthopedic screw 36.
• the through axial cavity 30 can also be made later, by means of perforation, once the attachment pre-insert 24 has been assembled in the plate 1 1 .
• a first step of assembling the attachment insert 14 provides to screw the attachment pre-insert 24 into a relative through hole 12 of the plate 1 1 .
• This operation is advantageously possible thanks to the mechanical resistance given by the composite material used, which supports the clamping forces, generally in the range of about 10 - 1 5 N/m, required for this type of application, unlike the traditional inserts made of simple polymeric plastic material which w ould inevitably be deformed in this operation.
• the second portion 28 substantially occupies the space of the through hole 12, remaining in the transverse bulk of the plate 1 1 , while the first portion 26 remains protruding from the lying plane P of the plate 1 1 .
• the attachment pre-insert 24 is worked so as to completely remove the first portion 26 and make it substantially flush with the plate 1 1 , so that the second portion 28, w hich will fonn the attachment insert 14, remains screwed into the through hole 12, comprised in the transverse bulk of the plate 1 1 .
• the through axial cavit 30 is also made, optionally provided with a pre-threading. This working is also intended to obtain the geometric configuration of the attachment insert 14 with the first segment 18 flared and the second segment 20 parallel to the central axis Y (fig. 8).
• an orthopedic screw 36 can be screwed into the attachment insert 14.
• the screw 36 traditionally comprises a head 40 and a shaft 41 .
• the shaft 41 may comprise tw o segments 38, 42, of which a first segment, next to the head 40, has a first diameter, and a second segment 42 has a second diameter, smaller than the first diameter.
• the different double diameter is advantageous to increase the application range of the polyaxial screws, allowing to maneuver better when the screw is inserted, increasing the possible variation of the angle and allow ing to position the screw with several angles.
• the present invention can also advantageously be used with polyaxial screws.
• the inclination of the orthopedic screw 36 can have its axis X perpendicular to the lying plane P of the plate 1 1 (fig. 1 1 ), or with axis X' inclined by a first angle a, for example in the case of fig. 12 about 10°, or with axis X" inclined by a second angle ', for example in the case of fig. 13 about 20°.
• the radio-transparency properties of the composite material in question are advantageous also for verifying the inclination of the screw s.
• the outer dimensions of the annular insert can be even greater than a traditional insert, for the purposes of increasing the radio- transparency window, as can be seen in fig. 1 5, with obvious advantages in verify ing the position of the screw s in the event of an inclined insertion, as is the case of the orthopedic screw 36 inserted inclined as in figs. 14 and 1 5.
• the increased sizes of the annular insert 1 14 are allowed by the greater mechanical resistance conferred by the composite material used in the present invention.
• Fig. 16 shows an advantageous form of embodiment of the present invention, indicated for convenience by the reference number 2 10.
• a plate 2 1 1 is made with traditional through holes 12, into which the attachment inserts 14 as above can be screwed, and also with a through hole 2 12 with a wider conformation, substantially comparable with the bulk in width of part of the plate 1 1 , into which an insert 214 is inserted, made of composite material as described above, with a mating shape and which has a plurality of attachment holes 1 16, each of a size correlated to the orthopedic screws to be used.
• the insert 214 can be coupled with the through hole 2 12 in any known manner, snap- in, interference, hooking or other,
• the insert 214 defines a bigger area of composite material, in which a desired distribution of attachment holes 1 16 is provided, and hence of constraining points between the plate 2 1 1 and the bone fragments to be recomposed, according to the needs of the surgical operation to be performed, Furthermore, in this case too there is the advantage of increasing the area of visibility or radio-transparency in order to verify the angular position of the orthopedic screws.
• Fig. 18 shows a comparative graph between the mechanical properties of elastomers, plastic polymers, such as PEEK, bone cortex, bio-compatible metals commonly used in the orthopedic field, typically titanium or its alloys, composite materials with a polymeric matrix base with reinforcement elements, such as PEEK loaded with carbon fibers, ceramics.
• Fig. 19 shows a comparative graph of the resistance to traction for bone cortex, composite PEEK reinforced with carbon fibers, PEEK, polyethylene.
• Fig. 20 shows a comparative graph of the resistance to flexion for extruded polyamide with 30% fiber glass (PA 6 30% glass), aluminum, steel used for the construction of tubes (ST 37), structural steel used for mechanical components (CK 45), composite PEEK reinforced with carbon fibers, both at 30% and at 60%.

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• Health & Medical Sciences (AREA)
• Orthopedic Medicine & Surgery (AREA)
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Citations (8)

• 2011
  • 2011-01-10 SM SM201100002A patent/SM201100002B/it unknown
• 2012
  • 2012-01-09 WO PCT/IB2012/000016 patent/WO2012095720A1/en active Application Filing

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